"Routine prevention of attacks of hereditary angioedema is an important therapeutic option for many patients," commented Prof. Dr. med. Marcus Maurer, Department of Dermatology, Venerology and Allergy, Charite University Medicine Berlin, Germany and principal investigator of the study in Germany. "While the current IV formulation of Cinryze is an important option for patients seeking to prevent their attacks, a subcutaneous formulation could represent a more convenient alternative for many."

This double blind, cross-over, dose ranging study will be conducted in approximately 40 adolescent and adult subjects in the U.S. and Europe. Qualified subjects will be randomized into one of two 8-week treatment sequences of either 1000 U Cinryze with 24,000 U rHuPH20 or 2000 U Cinryze with 48,000 U rHuPH20 as a twice weekly SC injection. Each subject will participate for approximately 6 months. The primary efficacy endpoint is the normalized number of angioedema attacks recorded during each treatment period. In addition, several secondary endpoints will be assessed, including attack severity, quality of life parameters using a novel angioedema tool, and number of angioedema attacks requiring acute treatment. Additional information about this Phase 2 subcutaneous Cinryze clinical trial can be found at clinicaltrials.gov.

"Our goal is to optimize the delivery and convenience of self administration of Cinryze, and we believe that the combination with rHuPH20 offers us the best opportunity to achieve that goal," commented Jennifer Schranz, MD, ViroPharma's vice president, clinical research. "The initiation of this important phase 2 study is an essential step toward continually enhancing the Cinryze experience for all patients who seek greater control over their disease through routine prevention."

About Cinryze® (C1 esterase inhibitor [human])

Cinryze is a highly purified, pasteurized and nanofiltered plasma-derived C1 esterase inhibitor product. In the U.S. and Canada, Cinryze is approved for routine prophylaxis (prevention) against angioedema attacks in adolescent and adult patients with HAE. In the E.U., the product is approved by the EMA for the treatment and pre-procedure prevention of angioedema attacks in adults and adolescents with hereditary angioedema (HAE), and routine prevention of angioedema attacks in adults and adolescents with severe and recurrent attacks of hereditary angioedema (HAE), who are intolerant to or insufficiently protected by oral prevention treatments or patients who are inadequately managed with repeated acute treatment. Cinryze is for intravenous use only.

Severe hypersensitivity reactions to Cinryze may occur. Thrombotic events have occurred in patients receiving Cinryze, and in patients receiving off-label high dose C1 inhibitor therapy. Monitor patients with known risk factors for thrombotic events. With any blood or plasma derived product, there may be a risk of transmission of infectious agents, e.g. viruses and, theoretically, the CJD agent. The risk has been reduced by screening donors for prior exposure to certain virus infections and by manufacturing steps to reduce the risk of viral transmission including pasteurization and nanofiltration.

The most common adverse reactions in clinical trials associated with Cinryze were rash, headache, nausea, erythema, phlebitis and local reactions at the injection site. Adverse events of sinusitis and upper respiratory infection also were observed in clinical trials. No drug-related serious adverse events (SAEs) were reported in clinical trials.

Enhanze is Halozyme's proprietary drug delivery platform based on the Company's patented recombinant human hyaluronidase enzyme (rHuPH20). rHuPH20 acts by removing traditional limitations on the volume of drugs that can be delivered subcutaneously (just under the skin). By using Enhanze, some drugs that are administered intravenously may instead be delivered subcutaneously. Enhanze may also benefit subcutaneous drugs by reducing the need for multiple injections. This improved delivery may improve patient convenience and reduce overall costs to the healthcare system.

About Hereditary Angioedema (HAE)

HAE is a rare, severely debilitating, life-threatening genetic disorder caused by a deficiency of C1 inhibitor, a human plasma protein. This condition is the result of a defect in the gene controlling the synthesis of C1 inhibitor. C1 inhibitor maintains the natural regulation of the contact, complement, and fibrinolytic systems, that when left unregulated, can initiate or perpetuate an attack by consuming the already low levels of endogenous C1 inhibitor in HAE patients. Patients with C1 inhibitor deficiency experience recurrent, unpredictable, debilitating, and potentially life threatening attacks of inflammation affecting the larynx, abdomen, face, extremities and urogenital tract. Patients with HAE experience approximately 20 to 100 days of incapacitation per year. There are estimated to be at least 6,500 people with HAE in the United States and at least 10,000 people in the European Union.

For more information on HAE, visit the HAEi's (International Patient Organization for C1 Inhibitor Deficiencies) website at www.haei.org and the U.S. HAE Association's website at: www.haea.org.

About ViroPharma Incorporated

ViroPharma Incorporated is an international biopharmaceutical company committed to developing and commercializing novel solutions for physician specialists to address unmet medical needs of patients living with diseases that have few if any clinical therapeutic options, including C1 esterase inhibitor deficiency, pediatric epilepsy and C. difficile infection (CDI). Our goal is to provide rewarding careers to employees, to create new standards of care in the way serious diseases are treated, and to build international partnerships with the patients, advocates, and health care professionals we serve. ViroPharma's commercial products address diseases including hereditary angioedema (HAE) and CDI; for prescribing information on our products, please download the package inserts at http://www.viropharma.com/Products.aspx.

ViroPharma routinely posts information, including press releases, which may be important to investors in the investor relations and media sections of our company's website, http://www.viropharma.com/. The company encourages investors to consult these sections for more information on ViroPharma and our business

About Halozyme

Halozyme Therapeutics is a biopharmaceutical company dedicated to developing and commercializing innovative products that advance patient care. With a diversified portfolio of enzymes that target the extracellular matrix, the Company's research focuses primarily on a family of human enzymes, known as hyaluronidases, that increase the absorption and dispersion of biologics. Halozyme's pipeline addresses therapeutic areas, such as diabetes, oncology and dermatology that have significant unmet medical need. The Company markets HYLENEX® recombinant (hyaluronidase human injection) and has partnerships with Roche, Baxter, ViroPharma and Intrexon. Halozyme is headquartered in San Diego, CA. For more information on how we are innovating, please visit our corporate website at www.halozyme.com

Forward Looking Statements

Certain statements in this press release contain forward-looking statements that involve a number of risks and uncertainties. Forward-looking statements provide our current expectations or forecasts of future events, including the therapeutic indication and use, safety, efficacy, tolerability, convenience of subcutaneous administration, and potential of Cinryze and our focus, goals, strategy, research and development programs, and ability to develop pharmaceutical products, commercialize pharmaceutical products, and execute on our plans including clinical development activities with Cinryze related to subcutaneous administration. There can be no assurance that that our clinical program with Cinryze utilizing subcutaneous administration in combination with rHuPH20 will yield positive results, be viewed by patients as more convenient than IV administration, or support further development of Cinryze for subcutaneous administration in combination with rHuPH20. The FDA or EMA may view the data regarding subcutaneous administration of Cinryze in combination with rHuPH20 as insufficient or inconclusive, request additional data, require additional clinical studies, delay any decision past the time frames anticipated by us, limit any approved indications, or deny the approval of Cinryze for subcutaneous administration in combination with rHuPH20. These factors, and other factors, including, but not limited to those described in our annual report on Form 10-K for the year ended December 31, 2010 and 10-Q filings for the quarters ended March 31, 2012, June 30, 2012, and September 30, 2012 filed with the Securities and Exchange Commission, could cause future results to differ materially from the expectations expressed in this press release. The forward-looking statements contained in this press release are made as of the date hereof and may become outdated over time. ViroPharma does not assume any responsibility for updating any forward-looking statements. These forward looking statements should not be relied upon as representing our assessments as of any date subsequent to the date of this press release.